On Snake and Chris Redfield:
thing is, the most unrealistic thing about these characters being constrained by the videogame medium, its that even if you throw out all their unrealistic in game feats, there is still the fact that you save and reload. its very likely that no player ever gets it right on the first time, so when they die they reload and try again until they do, when realistically, life just happens and you never get do-overs like that. so all realistic portrayal of human effort stops when a character dies then basically restarts from an earlier point to do it again but better. meaning these characters aren't realistic at all, they are constantly dying and rewinding gods whose only limit is how much they are willing to try and do before they decide to stop for a while.

so even if you discard all other feats as being unrealistic, there is still the fact that are beings who can keep trying again and again until they win and therefore in no actual danger of being defeated permanently.